With constant advancement of the science and technology, in recent years, more and more humanized operation interfaces are designed for various electronic products. For example, over a touch panel, a user may operate or input information/texts/graphics on the screen with a finger or a stylus, which save the trouble of using such an input device as a keyboard or a keypad. In practice, the touch panel is typically including a sensing panel and a display arranged at the rear of the sensing panel. An electronic device judges the intension of a touch according to the position of the touch on the sensing panel and the image presented by the display, and performs a corresponding operation.
The capacitive touch technology judges a touch event by sensing the capacitance variation of a detection capacitor in a detection circuit. The conventional capacitive touch technology may be categorized into self-capacitance touch technology and mutual-capacitance touch technology. The capacitance sensing circuit in a self-capacitance touch panel or a mutual-capacitance touch panel is capable of converting the capacitance of the detection capacitor into an analog output signal, and converting the analog signal into a digital signal by using an analog-to-digital converter, thus for the judgment and determination of a capacitance judging circuit at the rear end. However, regardless of the self-capacitance touch panel or the mutual-capacitance touch panel, the capacitance variation of the detection capacitor thereof is tiny, such that the analog output signal is subject to the capacitance variation and thus the generated signal variation is correspondingly small. From another aspect, the analog output signal may include a fixed signal and a variable signal, wherein the variable signal is the signal variation when the analog output signal is subject to the capacitance variation. The capacitance sensing circuit judges the capacitance variation of the detection capacitor according to the variable signal in the analog output signal. In other words, the variable signal caused a significant effect on capacitance sensing. For a correct analysis of capacitance changes of the detection capacitor, in the related art, the analog output signal is parsed by using an analog-to-digital converter having a large dynamic range and a high resolution. As a result, the complexity and manufacture cost of the circuit are increased. In addition, the large dynamic range and high resolution of the analog-to-digital converter are mostly consumed in parsing the fixed signal portion of the analog output signal. However, the variable signal which is significant to capacitance sensing may not be parsed. Therefore, some improvements to the related art are desired.